Armed with a device that looks like an old transistor radio, some Beijing residents are recording pollution levels and posting them online. It's an act that borders on subversion.

The government keeps secret all data on the fine particles that shroud China's capital in a health-threatening smog most days. But as they grow more prosperous, Chinese are demanding the right to know what the government does not tell them: just how polluted their city is.

"If people know what their air is like, they are more likely to take action," said Wang Qiuxia, a researcher at local environment group Green Beagle, who shows interested residents how to test pollution on a locally made monitoring machine. Continue reading.

Andy Wong / AP

Tan Liang carries a PM2.5 detector towards a garbage-burning facility located near his residential compound in Beijing on Dec. 3, 2011.

Andy Wong / AP

Wang Qiuxia, right, a volunteer from an environmental group, teaches Cheng Jing, left, how to operate the PM2.5 detector in Beijing on Dec. 7, 2011.